Fourie et al. Parasites Vectors (2019) 12:139 https://doi.org/10.1186/s13071-019-3393-z Parasites & Vectors RESEARCH Open Access A study on the long-term efcacy of Seresto® collars in preventing Babesia canis (Piana & Galli-Valerio, 1895) transmission to dogs by infected Dermacentor reticulatus (Fabricius, 1794) ticks Josephus J. Fourie1* , Christa de Vos1, Dionne Craford1, Matthias Pollmeier2 and Bettina Schunack2 Abstract Background: An imidacloprid/fumethrin collar (Seresto®) was previously shown to prevent infection with Babesia canis, transmitted by Dermacentor reticulatus, in dogs for up to 1 month after application. The present study evaluated the prevention of transmission throughout the claimed efcacy period of 8 months. Methods: Eight animals each were randomly included in groups 1 (negative control) and 2 (Seresto® collar), respec- tively. Animals in group 2 received the Seresto® collar on Day 0. Tick challenges were performed monthly from the 2nd to the 8th month. Assessment criteria included in situ tick counts 48 hours post-challenge, polymerase chain reaction (PCR) analyses and immunofuorescence assays (IFA). Whenever dogs were diagnosed with babesiosis they were “rescue-treated”, excluded and replaced. Consequently, 24 replacement animals were introduced at various time points throughout the study in the control group; thus data for a total of 32 dogs were available in the latter group at study termination. Results: Acaricidal efcacy for in situ counts was 93% on Day 30, and ranged from 97 to 100% thereafter. No B. canis specifc DNA or antibodies were detected in any Seresto®-treated dog at any time. Babesia canis-specifc DNA and antibodies were detected in 2–6 of 8 control dogs after each challenge, confrming the validity of the challenge model. Conclusions: The Seresto® collar was highly efective against challenges with D. reticulatus ticks for up to 8 months. The high sustained acaricidal efcacy over this period prevented transmission of B. canis, thus fully protecting dogs against infection in this experimental infestation model. Keywords: Seresto®, Imidacloprid, Flumethrin, Babesia canis, Dermacentor reticulatus, Transmission prevention Background Babesia spp., with the species relevant to Europe being: Worldwide, ticks transmit a broad range of diseases B. canis, B. vogeli, B. gibsoni, and B. microti-like isolates to dogs of which canine babesiosis is one of the most also referred to as “B. vulpes” and “Teileria annae” [1]. signifcant and clinically relevant. Clinical disease is Te clinical signs, treatment and prognosis of infec- caused by infections with both large and small forms of tions with these Babesia spp. vary greatly, and the transmission and geographical distribution is mainly based on that of the competent tick vectors. In general, *Correspondence: [email protected] it is assumed that the least pathogenic large-sized spe- 1 Clinvet International (Pty) Ltd, Uitzich Road, Bainsvlei, Bloemfontein, South Africa cies of Babesia is B. vogeli, and that the most virulent Full list of author information is available at the end of the article species in Europe is B. canis, transmitted mainly by © The Author(s) 2019. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creat iveco mmons .org/licen ses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creat iveco mmons .org/ publi cdoma in/zero/1.0/) applies to the data made available in this article, unless otherwise stated. Fourie et al. Parasites Vectors (2019) 12:139 Page 2 of 8 the ornate dog tick, Dermacentor reticulatus [2]. Tis Efective protection of dogs against infection not only Babesia sp., like others in its genus, is able to invade relies on an immediate rapid killing efect, but also on ovaries of female D. reticulatus ticks and is transmitted sustaining this rapid killing efect over the entire period transovarially to the next generation of larvae. Together during which ticks are active in the environment, irre- with transstadial transmission, this feature results in spective of a dog’s lifestyle (e.g. frequent swimming). D. reticulatus populations functioning as a reservoir, Acaricidal collars with long-lasting sustained efcacy enabling maintenance of B. canis locally for several tick have been widely used against ticks on companion ani- generations [3]. Dermacentor reticulatus is widely dis- mals and may be ideally suited to protect dogs against B. tributed over central Europe, but in recent years its dis- canis infection, if the rapid killing efect can be sustained tribution has considerably expanded in some regions. over these long periods of efcacy [17–19]. Te rapid Large areas thought to be historically too cold for its killing efect of the Seresto® collar (imidacloprid 10%/ survival and completion of its life-cycle, have now been fumethrin 4.5%), with a proven sustained high level of invaded by this tick. Countries that have experienced efcacy against ticks [20], has previously been shown to a remarkable spread of this tick are Germany, Poland, efectively prevent infection with B. canis after a single Hungary and Slovakia, but also the Netherlands and challenge one month after collar application [11]. Conse- Belgium, with the recent climatic changes being fre- quently, this collar may have the potential to prevent the quently reported as the predominant driving force [4, transmission of B. canis by infected ticks over the entire 5]. Other factors contributing to the spread of this tick claimed efcacy period of eight months, making it an are its wide host range that includes wild and domes- ideal candidate for protecting dogs against canine babe- ticated mammals, and its extreme environmental sur- siosis over the entire tick activity season. Te objective of vivability and tolerance. Adult ticks have been shown to the study was to determine the efcacy of the Seresto® survive for up to four years without a blood meal, toler- collar in the prevention of transmission of B. canis by ate extreme cold (−10 °C for 150 days under laboratory infected D. reticulatus ticks to dogs, for a time period conditions), and even when submerged in cool clean consistent with the claimed efcacy period of eight water adult ticks survived for more than 100 days [6– months. 8]. For the European market, a vaccine for dogs against B. canis is available, based on soluble parasite antigens Methods that induce a partial protection for dogs newly exposed General design to B. canis. Vaccination does not prevent infection, Te study was designed as a parallel group, randomised, but both shortens and diminishes the severity of their single centre, negative controlled, efcacy study, and was clinical signs; moreover, a lower parasitemia may result. conducted in compliance with the VICH GL9 on Good Vaccination can be started from fve months of age and Clinical Practice and was approved by an institutional requires annual re-vaccination, but does not cross- animal care and use committee (Clinvet IACUC). Te protect against other Babesia spp. Te protection of study employed two groups, non-treated control group 1 dogs against infection with B. canis therefore primarily and Seresto®-treated group 2, each consisting of 8 dogs. relies on the efective on-host control of the tick vector, All dogs were acclimatized to the cage environment for thereby also reducing the tick population in the envi- at least 7 days before inclusion and random allocation ronment capable of transmitting infections. to their study groups was based on body weight. Dogs To efectively prevent B. canis infections, rapid killing in group 2 were ftted with the Seresto® collar on Day of ticks on the dog is required. As such, ticks need to be 0 and all dogs (groups 1 and 2) were subsequently chal- killed before maturation of the B. canis sporozoites pre- lenged monthly with ticks starting on Day 28. Dogs were sent in their salivary glands, which has been reported to observed daily for general health. In addition, monthly take up to 48 hours after attachment [9]. tick counts, blood sampling and frequent veterinary Once a D. reticulatus tick has taken a blood meal and examinations were performed (see activity schedule in feeding is interrupted, transmission time is shortened Table 1). and was shown to have occurred within eight hours as demonstrated for male D. reticulatus [10]. Te develop- Animals ment of challenge models with unfed infected labora- Purpose-bred dogs, identifed using electronic tran- tory bred ticks made it possible to assess the efcacy of sponders with unique alphanumeric codes and belonging acaricidal products to prevent transmission of B. canis, to Clinvet International (Pty) Ltd, were used in the study. which has been demonstrated for several treatments At the time of enrolment all dogs were between 6 months such as topically applied contact acaricides [11–13], and and 6 years of age, and weighed between 10.2 and 31.6 more recently systemic isoxazoline compounds [14–16]. kg. Dogs were ranked within sex by body weight. Within Fourie et al. Parasites Vectors (2019) 12:139 Page 3 of 8 Table 1 Activity schedule Tick challenges Tick counts Blood sampling Clinical examinations Days 28, 56, 84, 112, 140, 168, In situ counts on Days 30, 58, 86, 114, IFA: Prior to inclusion and on Days-7, 28, 56, 84, 112, Day-7 and weekly 196 and 224 142, 170, 198 and 226. Removal 140, 168, 196, 224 and 252; thereafter up to Day count on Day 231 PCR: Following positive diagnosis on blood smears, 252 as well as Day 252 for dogs where no infection was observed thus far blocks of two, dogs were randomly allocated to the Rectal body temperatures were recorded three times per respective study groups.